Graphene materials are graphite materials in nanoscale formed by a single-layer graphite. As regards a porous graphene, a number of pores in nanoscale are prepared on graphene sheets by using a physical or chemical method. A porous structure makes graphene advantageous in aspects of energy, catalytic or adsorption materials.
At present, the graphene material with porous structure is prepared by the mainly following methods: (1) adding a multi-layer graphene and a surfactant into a strong alkaline aqueous solution for a hydrothermal reaction, which however introduces many functional groups into the graphene sheets due to an addition of the surfactant; (2) simultaneously heating a carbon material such as graphene and a transition metal to obtain the porous graphene, however the transition metal used in such method is expensive; (3) obtaining the graphene sheets by a chemical deposition method and then forming the porous graphene by means of etching, which however is complicated in process and has a high cost; and (4) mixing graphite with nano metal particles, and obtaining the porous graphene material by dissolving with an acid, which however increases a cost of the reaction due to an introduction of nano metals. In the present invention, by means of an ultrasonic treatment in one step, the porous graphene is prepared and a graphene quantum dot is obtained simultaneously. Such method is simple to perform and has a low cost. Further, by this method, the porous graphene having a high degree of graphitization, fewer layers and a larger lateral dimension of sheet is obtained.
In addition to the excellent properties of graphene, the graphene quantum dot further exhibits a series of new properties due to the quantum confinement effect and the boundary effect. The preparation methods for the graphene quantum dot are categorized into two types, a top-down method and a down-top method. The top-down method mainly includes a hydrothermal method, an electrochemical method and a chemical peeled carbon fiber method. A starting material used in these methods is generally graphene oxide or reduced graphene oxide. During the preparation, a strong oxidant or a toxic reagent is used. The down-top method mainly includes a solution chemical method, an ultrasonic wave method, a microwave method and a controllable thermal degradation of polycyclic aromatic hydrocarbon, wherein small molecules are used as a carbon source to prepare a carbon quantum dot. An ultrasonic etching method is also one of the top-down methods. At present, there is no report teaching preparation of the porous graphene and the graphene quantum dot by means of the ultrasonic treatment in one step with graphite as the starting material.